Free Calendar Heatmap Generator
Turn your date,value data into a GitHub-style calendar heatmap, pick a palette, and download a crisp PNG or SVG. No signup, no watermark.
237 days parsed. Paste your own CSV, or export from a spreadsheet as date,value per line.
What is a calendar heatmap?
A calendar heatmap is a grid of days colored by a daily value, laid out in week columns with month and weekday labels. It's the GitHub contribution graph pattern, and it makes streaks, gaps, and busy periods obvious across a whole year at a glance.
How to make a calendar heatmap
- 1Add your data. Paste one day per line as date,value, or click load sample year to start. Dates use the YYYY-MM-DD format.
- 2Pick a color mode. Use ramp for a single-hue intensity scale like the GitHub green, or diverging to color positive and negative days for returns.
- 3Pick a palette and background. Choose from GitHub green, blue, purple, or amber, on a light or dark card.
- 4Download PNG or SVG. Click download for a high-resolution PNG or a crisp, scalable SVG. No watermark and no signup.
- 5Automate with the API (optional). Save it as an Imejis template and generate the same heatmap from live data on every API call.
What is a calendar heatmap used for?
- GitHub-style contribution and activity graphs
- Streak and habit-tracker cards
- Daily-metric summaries like signups or sales over a year
- Daily returns or net-change calendars for finance
- Any per-day value you want to see across a full year
How this chart maker compares
| Feature | This tool | Chart-image APIs | Design makers |
|---|---|---|---|
| No-code visual editor | Yes | No, write JSON/URL config | Yes |
| Chord + 23 other chart types | Yes | Limited / plugins | Some types only |
| PNG and SVG export | Yes, free | Varies, often watermarked free | Often account-gated |
| No signup, no watermark | Yes | API key required | Account required |
| Matching image API | Yes | API only, no editor | No |
Bottom line: config-driven chart APIs make you hand-write JSON and live with dated defaults, and design makers gate exports behind an account. This tool gives you a live editor, beautiful output, free PNG and SVG, and the same chart on tap via API.
Generate calendar heatmaps automatically via API
Save your design as a template, mark the calendar component dynamic, and render the same heatmap with fresh data on every API call. It is the only calendar heatmap tool with a matching image API.
See the calendar component and API